# Example: Christmas fractal tree

Published 2011-12-24 | Author: Andrew Stacey
Posted for celebrating Christmas 2011 on TeX.SX.

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% A Christmas tree
% Decorations by Andrew Stacey
% Based on a fractal tree (L-System) drawn in TikZ by Stefan Kottwitz
% Tree example from the book "The Science of fractal images" by Peitgen and Saupe.
\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{%
lindenmayersystems,
decorations.pathmorphing,
decorations.markings,
shapes.geometric,
calc%
}
\tikzset{
tinsel/.style={
#1,
rounded corners=10mm,
ultra thin,
decorate,
decoration={
snake,
amplitude=.1mm,
segment length=10,
}
},
baubles/.style={
decorate,
decoration={
markings,
mark=between positions .3 and 1 step 2cm
with
{
\pgfmathsetmacro{\brad}{2 + .5 * rand}
}
}
},
lights/.style={
decorate,
decoration={
markings,
mark=between positions 0 and 1 step 1cm
with
{
\pgfmathparse{rand > 0 ? "dart" : "kite"}
\let\lshape\pgfmathresult
\pgfmathsetmacro{\tint}{100*rnd}
\node[rotate=90,\lshape,shading=ball,inner sep=1pt,ball color=red!\tint!yellow] {};
}
}
}
}

\begin{document}
\begin{tikzpicture}
\coordinate (star) at (0,-1);
\path (star) +(-50:7) coordinate (rhs) +(-130:7) coordinate (lhs);
\draw[brown!50!black,line width=5mm,line cap=round] (star) ++(-90:6.8) -- ++(0,-1) coordinate (base);
\node[scale=-1,trapezium,fill=black,minimum size=1cm] at (base) {};
\foreach \height/\colour in {%
.2/blue,
.4/yellow,
.6/red,
.8/orange,
1/pink%
} {
\draw[tinsel=\colour] ($(star)!\height!(lhs)$) to[bend right] ($(star)!\height!(rhs)$);
}
\path (star);
\pgfgetlastxy{\starx}{\stary}
\begin{scope}[xshift=\starx,yshift=\stary,yshift=-7cm]
\draw[color=green!50!black, l-system={rule set={S -> [+++G][---G]TS,  G -> +H[-G]L, H -> -G[+H]L, T -> TL, L -> [-FFF][+FFF]F}, step=4pt, angle=18, axiom=+++++SLFFF, order=11}] lindenmayer system -- cycle;
\end{scope}
\foreach \height/\colour in {%
.1/pink,
.3/red,
.5/yellow,
.7/blue,
.9/orange%
} {
\draw[tinsel=\colour] ($(star)!\height!(lhs)$) to[bend right] ($(star)!\height!(rhs)$);
}
\foreach \height in {.15,.35,...,1} {
\draw[lights]  ($(star)!\height!(lhs)$) to[bend right] ($(star)!\height!(rhs)$);
}
\foreach \angle/\colour in {
-50/red,
-70/yellow,
-90/blue,
-110/pink,
-130/purple%
} {
\draw[baubles=\colour] (star) -- ++(\angle:7);
}
\node[star,star point ratio=2.5,fill=yellow,minimum size=1cm] at (star) {};
\end{tikzpicture}
\end{document}


• #1 Helmut Haase, December 28, 2011 at 6:21 p.m.

A beautiful excercise! But not for beginners.

I am just digging into tikz.

Kind regards

Helmut

• #2 Stefan Kottwitz, December 29, 2011 at 1:19 a.m.

Hi Helmut!

Yes, it's a bit playful regarding the decorations. The tree itself is easy to draw, once you know the L-System rules:

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{lindenmayersystems}
\begin{document}
\begin{tikzpicture}
\draw [color=green!50!black,
l-system={rule set={S -> [+++G][---G]TS,
G -> +H[-G]L, H -> -G[+H]L, T -> TL,
L -> [-FFF][+FFF]F}, step=4pt, angle=18,
axiom=+++++SLFFF, order=11}]
lindenmayer system -- cycle;
\end{tikzpicture}
\end{document} 